It has already been proposed to use quaternary ammonium salt compounds or quaternary ammonium salt-series polymers in hair-conditioning cosmetics, such as a shampoo, a rinse, a hair treatment, a wavesetting lotion, etc., as disclosed in U.S. Pat. Nos. 3,934,595; 4,030,512; 3,836,537 and 4,075,131, and Japanese Patent Publication Nos. 11128/80 and 17009/80.
As the quaternary ammonium salt compounds, are known stearyl-trimethylammonium chloride, lauryl-trimethylammonium chloride, distearyl-dimethylammonium chloride, etc. As the quaternary ammonium salt-series polymers, are known dimethylaminoethyl methacrylate-series quaternary ammonium salt polymers, diallyl-dimethylammonium chloride-series polymers, cationic celluloses, etc.
The quaternary ammonium salt compounds have the double advantage of making the hair easier to comb and of softening it. However, the cmpounds have the disadvantage of losing the voluminousness of the hair, of losing the settlement of the hair and of making it more difficult to set. The quaternary ammonium salt-series polymers have the advantage of making the hair easier to comb. However, the polymers have the disadvantage of giving a specific malaise to the hair, that is, losing a good feeling caused by the accumulation of the polymers onto the hair in the repetitious use thereof as a so-called build-up problem. Furthermore, these quaternary ammonium salt compounds and polymers have other disadvantages in compatibility with anion-charged compounds caused by the cation charge and hyperhygroscopicity of the quaternary ammonium salt group, in the feeling of the hair at high temperature and humidity, in the worsening of the hair's condition, in the rapidly losing of the wavesetting property, etc.
On the other hand, although being useful for setting the hair, the zwitterionic polymers according to the prior art are not useful for conditioning hair.
After extensive investigations in order to solve the above-mentioned problems, the inventors of this application have found that a specific zwitterionic copolymer shows an excellent hair-conditioning effect.